Old house borers

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Old House Borer

Order/Family: Coleoptera/Cerambycidae

Scientific Name: Hylotrupes bojulus (Linnaeus)

Description: Old house borers are members of a large beetle family called the long-horned beetles, named because of their long antennae which are about one-third the body length (or longer). The adult insects are large beetles, approximately 5/8- to 1-inch long. Adult old house borers are slightly flattened, brownish-black with gray or yellow-gray hairs on the upper surface of the body which may be rubbed off the older beetles. The first body segment behind the head (prothorax) has two raised, black, shiny knobs on the upper surface that look like a pair of eyes. The hard wing covers have two wavy, light colored lines that cross them from side to side about one-third of the way down their length.

Old house borer larvae are worm-like, creamy-white, and up to 1-1/4-inches long when mature. They have a broad prothorax which tapers spindle-like to the abdomen. The abdominal segments have deep folds between them so that the abdomen looks as if it is composed of a series of large beads. This stage has prominent chewing mouthparts and very tiny legs on the first body segments (thorax). Old house borer larvae have three simple black eyes (ocelli) in a row at the base of each antenna.

Biology: Adults emerge in early summer to mate, and the females lay 40 to 50 eggs in checks, cracks, or crevices of suitable wood. The hatched larvae bore into the wood and develop during the next two to 10 years with the majority taking from three to five years to reach the pupal stage. The pupal stage lasts only about two weeks, but the new adults remain in the tunnels for seven to 10 months before emerging through oval holes which are 3/8-inch at their widest diameter. Adults live approximately 16 days.

Habits: Old house borers can infest old and new houses. They are the only long-horned beetles that infest seasoned lumber. Old house borer larvae feed only on coniferous lumber such as pine, spruce, fir, and hemlock. The rasping and ticking of the larval feeding activity often is heard by building-occupants and is one of the first signs of an infestation. The galleries are filled with fine frass mixed with small bun-shaped pellets. The surface of infested wood often has a wavy, blistered appearance.

Control: Old house borer infestations are discovered by hearing the larvae feeding in the wood, finding larvae in the wood, seeing accumulating frass, discovering the emergence holes, and seeing adult beetles. Determine if the infestation is active and then recommend treatment. Infested wood can be removed and replaced with treated wood. Reducing the wood moisture content to less than 10% slows the development of the larvae and often kills.

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